Renaturation kinetics of cDNA complementary to cytoplamic polyadenylated RNA from rainbow trout testis. Accessibility of transcribed genes to pancreatic DNase.

We have determined the fraction of polyadenylated cytoplasmic RNA from trout testis complementary to unique and repetitive DNA. Some 21% of the cDNA probe representative of this RNA population renatures with rapid kinetics, characteristics of repetitive sequences. The major proportion of the cDNA renatures with unique sequence DNA. Experiments with fractionated cDNA probes allow us to conclude that, in trout testis, the most abundant polyadenylated mRNAs are not preferentially transcribed from repetitive DNA, as it has shown to be the case in two eukaryotic cell lines. Treatment of trout testis nuclei with DNase I, under conditions in which 10% of the total DNA is digested, preferentially depletes the DNA of sequences being transcribed into polyadenylated mRNA. These data confirm the results of H. Weintraub and M. Groundine [(1976) Science 193, 848-856] and those of A. Garel and R. Axel [(1976) Proc. Natl. Acad. Sci. U.S.A. 73, 3966-3970] and suggest that the conformation of DNA in the active genes of chromatin is such that it is more susceptible to digestion by DNaseI.